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rootfind with p #125

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merged 3 commits into from
Oct 16, 2023
Merged

rootfind with p #125

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c3d0e5c
rootfind with p
lindnemi May 15, 2023
c20296a
add suggestions
lindnemi Oct 16, 2023
cbaf49f
fix keyword error
lindnemi Oct 16, 2023
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29 changes: 15 additions & 14 deletions src/Utilities.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -169,14 +169,15 @@ function find_fixpoint(nd, p, initial_guess)
return nl_res.zero
else
println("Failed to find fixpoint. Algorithm did not converge.")
println("Try running nlsolve with other options.")
end
end

export RootRhs

"""
struct RootRhs
RootRhs(of)
RootRhs(nd)

A utility function that provides a root function, to find valid initial
conditions. The operator ``M^\\dagger M - 1`` projects onto the kernel of ``M``.
Expand All @@ -187,36 +188,36 @@ by returning the projection of ``f(x)`` onto the kernel as residue.
The use of the pseudoinverse here means this does not play nice with sparse
matrices. Beware when using for large systems.
"""
struct RootRhs
rhs
mpm
struct RootRhs{T,S}
rhs::T
mpm::S
end
function (rr::RootRhs)(x)
function (rr::RootRhs)(x, p=nothing, t=nothing)
f_x = similar(x)
rr.rhs(f_x, x, nothing, 0.0)
rr.mpm * f_x .- f_x
rr.rhs(f_x, x, p, t)
return rr.mpm * f_x .- f_x
end

function RootRhs(of)
mm = of.mass_matrix
function RootRhs(nd)
mm = nd.mass_matrix
@assert mm !== nothing
mpm = pinv(mm) * mm
RootRhs(of.f, mpm)
return RootRhs(nd.f, mpm)
end


export find_valid_ic


"""
find_valid_ic(of, ic_guess)
find_valid_ic(nd, ic_guess)

Try to find valid initial conditions for problems involving mass matrices.
Uses RootRhs as residual function.
"""
function find_valid_ic(of, ic_guess)
rr = RootRhs(of)
nl_res = nlsolve(rr, ic_guess)
function find_valid_ic(nd, initial_guess; p=nothing)
rr = RootRhs(nd)
nl_res = nlsolve(x -> rr(x, p), initial_guess)
if converged(nl_res) == true
return nl_res.zero
else
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